Cutter-bit assemblies of various designs are widely used in mining and tunnelling operations. Normally, such assemblies are composed of a holder secured to a cutting appliance or machine, such as a coal plough, and a separate cutter-bit which is inserted into a pocket in the holder. To secure the cutter-bit within the holder it is known to employ a wedge element which jams a shank of the cutter-bit in the pocket. U.S. Pat. Nos. 4,456,307 and 4,626,034 and German Gebrauchsmuster No. G 35 18 045.9 describe assemblies which use an arcuate tapered wedge. During use however and especially when the assembly is subjected to impact stress, deformation and wear can cause loosening of the wedge and the cutter-bit and chattering and damage can occur. The service life of the cutter-bits can be improved significantly if the means used to secure the cutter-bits in the holders is made more reliable and the above-mentioned publications describe various measures which can be adopted to lock the arcuate wedge in position. Nevertheless, although such measures greatly reduce the tendency of the wedge to work loose this still occurs from time to time. A general object of the invention is to provide an improved form of cutter-bit assembly.